WASHINGTON
— WASHINGTON is starting to feel like a two-party town again.

On Capitol Hill, Democrats are getting more deft at playing Cassandra - warning of the dangers they see in Republican actions, even if they aren't always putting up alternatives themselves.

The role of contrarian is an unfamiliar one, especially in the House, where the left side of the aisle dominated for 40 uninterrupted years. For months Democrats seemed unable to come to terms with their new status. But lately they have turned to late-night guerrilla tactics, blocking key Republican bills and winning concessions with flurries of parliamentary procedures, amendments, and even a clumsy filibuster.

It is hard to tell whether these obstructionary tactics are products of strategy or chaos - whether the Democrats are finally emerging as an activated minority or just flailing about more vigorously. ''We're seeing signs that the Democrats are awakening,'' says Thomas Mann, a political analyst at the Brookings Institution.

The Democratic resurgence comes at a time when Republicans are trying to enact some of the most critical and controversial parts of their plan to balance the budget.

Minority leaders in the House insist that Democrats have banded together to protect ''ordinary Americans'' at a time when Republicans hope to rein in spending on Medicare and Medicaid to finance tax cuts for the wealthy.

During one recent assault, when Democrats kept the House in session all night, ''we had a midnight meeting and we really came together,'' says California Rep. Vic Fazio, the third-ranking House Democrat. ''I see it as a major turning point.''

Triumphal Republicans, no strangers to hardball tactics themselves, dismiss the Democrats' activated defiance. ''If that's the best thing they have in their arsenal,'' says Rep. Susan Molinari (R) of New York, ''We're going to be in the majority for a long time.''

When Congress broke for the week-long Fourth of July recess, Democrats had successfully prevented both the House and Senate from finishing key pieces of legislation. Not surprisingly, when lawmakers returned to Capitol Hill this week, things picked up right where they left off.

In the Senate, leaders on both sides sought to rein in two defiant junior Democrats who are preventing progress on a bill that cuts $16.3 billion from the current budget and provides emergency aid to California and Oklahoma City. Majority leader Bob Dole (R) of Kansas has vowed not to bring the bill back onto the floor until the Democrats agree to suspend further amendments.

In the meantime, the upper chamber began work on a sweeping regulatory reform bill that Senator Dole is personally championing. Here again, hardball tactics by the Democrats appear to be working.

The bill requires agencies to measure the cost of a new regulation against its environmental and health benefits and conduct risk assessments before imposing the new rule. It also allows industries greater leverage to challenge them.

Democrats had threatened to derail the bill, arguing that it would undermine the government's ability to protect the environment, ensure food quality, and safeguard the workplace. They also argued that agencies would be hamstrung by industry appeals.

Dole quipped that the Democrats were merely sowing fear, but late Tuesday agreed to adopt parts of a narrower Democratic alternative to avert legislative gridlock.

The new version, which could pass today, requires that a cost-benefit analysis and risk assessment be done before any new regulation is imposed that could cost industry $100 million or more to comply with.

Across the Rotunda, things haven't been quite so conciliatory. When Rep. Greg Laughlin, a Democrat from Texas, jumped the aisle late last month, his new Republican colleagues saw an opportunity that infuriated the Democrats.

GOP House leaders offered Mr. Laughlin something he had long coveted - a seat on the powerful Ways and Means Committee. The assignment is important. Among the committee's responsibilities is the task of writing the GOP plan to rein in spending on Medicare and Medicaid, the health-care programs for the elderly and poor. Tampering with these voter-sensitive programs entails some political risk.

House Democrats erupted, arguing the Republicans were putting Laughlin on the committee to provide cover for three GOP freshmen whose seats could be in jeopardy if they vote with the party to prune Medicare.

Rallying around the issue, Democrats delayed floor action for days on the Laughlin committee assignment and a bill to provide $12 billion for foreign assistance in the next budget year. And though they lost both fights this week, the battles appear to have galvanized the party caucus.

''We are deeply concerned about the Republican leadership's desire to stack Ways and Means to cut Medicare in order to pay for tax cuts to the wealthiest Americans,'' said Rep. Dick Gephardt, minority leader from Missouri.

''Democrats are for working people. We fight for people who need Medicare and student loans. This is about equity and fairness.''